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ENG
6. SELECTION OF VALVE AND ACTUATOR KITS
For pressurized steam systems, control valves are needed to regulate the
flow of steam to the ultimateSAM distributor. Flow regulation is achieved
by 3 actions.
1.
A humidity sensor/controller creates either an electrical or pneumatic
demand signal that modulates in proportion to the humidity deficit.
2.
The demand signal produces a corresponding change in the position
of the valve's actuator.
3.
The actuator's position causes a linear change of flow rate, thereby
tracking the humidity deficit.
For most applications, the control valve and actuator, such as the one shown
in Fig. 6.a, should have the following general characteristics:
•
Normally-closed
•
Stainless steel trim
•
Linear (or nearly linear) signal-to-output modulation
•
Spring-return to closed position during failure
In addition, several other factors must be considered when selecting the
proper control valve, including,
•
Humidification load (H)
•
Bottom or top feed distributor
•
Steam delivery pressure
•
Pressure drop across the valve
•
Steam quality requirements
The system for identifying control valve accessories is shown in Table 6.a.
Note: Not all of the possible combinations shown on the table are
available. A complete list of available valves, as well as information
on other features, is provided to 6.2 paragraph.
"ultimateSAM - design" +03U0071EF - rel. 2.0 - 20150301
Fig. 6.a
Fig. 6.b
SAKV 0
└──┬──┘ └┬┘ └┬┘ └┬┘ └┬┘ └┬┘ └┬┘
ID prefix
0
0
Material
F = Cast iron
S = Stainless steel
0 = Brass body with stainless steel (only for North America)
Operating
F = 0.1-4 bars (1.45-50psi )
pressure
Nominal size
A= 0.4
Kv (EU)
B= 0.63 (EU) B= 0.75 (North America)
Cv (US)
C= 1
D= 1.6 (EU) D=1.8 (North America)
E= 2.5 (EU) E = 2.9 (North America)
F= 4 (EU) F= 4.4 (North America)
G= 6.3
H= 10
I= 16
J= 25 (EU) J=24 (North America)
K= 40
L= 63 (Not available in North American market)
Region
U = North America
0 = Other
---
---
** Kv/Cv =63 not availble in North America.
Example 1: an SAKV0FHD00 valve includes the following:
•
Cast iron valve body with SS trim
•
Market outside of North America
•
Operating pressure up to 4 bar (58 psig)
•
Kv rating of 1.6
•
Flange PN 16 connections
Example 2: an SAKV00HIU0 valve includes the following:
•
Brass valve body with SS trim
•
North American market
•
Operating pressure up to 4 bar (50 psig)
•
Cv rating of 16
•
NPT connections for North American market
A flowchart illustrating a typical process for selecting the proper control
valve is shown in Figure 6.c.
•
In general, it is best to select the smallest valve that still has a maximum
flow rate greater than the humidification load (H). Valve flow capacity is
given in terms of the flow coefficient, Kv or Cv. Additional information on
valve sizing and flow coefficient is provided in Section 6.1.
•
Once the Kv or Cv of the valve is determined, the choice of material is
influenced by the operating pressure for the valve. For some applications,
regulations may require the use of valves having all stainless steel
construction.
24
x
x
x
x
0
Tab. 6.a
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